/**
 * 弹出框
 */
(function($) {
			jQuery.fn.extend({
				center : function(){
					var x = ($(document).height()-$(this).height())/2;
					var y = ($(document).width()-$(this).width())/2;
					this.css('position','absolute');
					this.css('top', x+"px");
					this.css('left',y+"px");
					this.show();
				},
				hidden : function(){
					this.hide();
				}
			});
})(jQuery);